At a time of increasing concern over pollution of the atmosphere, the land and the oceans, it is particularly important to develop means to provide for the energy needs of civilization without further creating pollution. This requires a system where energy is collected without by-products requiring disposal, such as carbon dioxide and carbon monoxide and other noxious gases as well as the ash from the burning of hydrocarbon fuels, whether gases, liquid petroleum or solid coal, or the disposal of radioactive wastes from nuclear reactor systems.
Amongst the many sources of pollution-free energy, hydroelectric power has perhaps been the most successful to date. However, even hydroelectric power requires a permanent change in the land and a loss of valuable landscape, as is shown by the controversies which have erupted as new power dam sites have been proposed or placed under construction. Perhaps the oldest dream, however, has been to harness the practically limitless and free energy available from sunlight, or solar radiation. This dream has been exemplified by many systems and methods for collecting, focusing and concentrating, and converting the solar radiation to a usable form of energy, preferably ultimately to generate electricity.
Solar energy collection devices have ranged from the relatively simple flat panels which are situated on the roofs of dwellings and other houses and generally provide within the flat panel numerous pipes for circulating water, which are than heated to provide hot water and heat to the house in the evening hours. In the more sophisticated designs, there is also a heat reservoir, generally located underground, to store the heat during those periods when sunlight is weak or at night.
Other more sophisticated devices have been designed and constructed for the generation of electricity by converting the sunlight first to heat and then applying the heat to boil a liquid to drive a turbine or other generator system. Finally, recently developed systems provide for the direct conversion of sunlight to electricity using photo-electric cells. Such units generally include means for greatly concentrating and focusing the sun's radiation as well as mechanical means for tracking the sun so as to maintain the focusing mechanism in the most desirable, i.e., perpendicular, position relative to the direction of the sun's rays.
Such focusing or concentrating collector means are described for example in U.S. Pat. Nos. 4,257,401; 4,168,696; 4,148,300; 4,038,971 and 4,011,858. Mechanical devices for tracking the sun and supporting the focusing collector are disclosed for example in U.S. Pat. Nos. 4,153,039; 4,068,653; 3,999,389 and 4,275,710, and 820,127.
These various systems provide reflecting and/or refracting focusing mirrors and lenses, such as parabolic reflectors and convex lens or fresnel-type lenses to focus and concentrate a relatively large surface area of incident radiation upon a small surface area which is to be heated, and mechanical means for tracking the sun.